This invention relates to a wind driven turbine and in particular to a wind driven turbine comprising a plurality of vanes which are arranged to rotate about a vertical axis.
Wind driven turbines and windmills have been known and used for many years, for example to pump water from boreholes on farms and in country areas.
Previously known turbines and windmills, which have rotated about a substantially horizontal axis, have had vertical vanes and have had the advantage that the vanes generate torque at all angular positions as they rotate. It has been found however, that a tower is normally necessary to provide ground clearance for such vanes. This has presented problems in that such vanes are often inaccessible for maintenance and repair. Further, such turbines have not always been as efficient and operable as operators and users would like.
Wind driven turbines and windmills which rotate about a substantially vertical axis are also known, although one disadvantage with known vertical axis turbines is that the vanes of rotors travelling in the direction of the wind often tend to shield one another, so that it is often inefficient and frustrating to use a multi-vane rotor. Further, in known vertical axis turbines the vanes of rotors, travelling into the wind on one side of the rotor, usually exert a torque opposite to that desired. Although this is reduced if the vanes are concave on one side and convex on the other, (the concave surface of the vane producing the dominant torque), the drag exerted on the rotor caused by the movement of the convex vane surfaces into the wind,, is often considerable Certainly such drag adversely affects the efficiency of such turbines.
It is an object of this invention to go at least some way towards overcoming or at least minimizing the above problems and to at least provide the public with a reasonable choice.